Induction furnace



March 10, 1931. N R DAV|$ 1,795,935

INDUCTION FURNACE Filed Jan. 8, 1930 Fig.1.

INVENTOR Neville R. Davis ATT'ORNEY Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE NEVILLE BYLAND DAVIS, OF ASHTON LANE, SALE, ENGLAND, ASSIGNOR TO WESTING- IEO'USE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 01' PENNSYL- VANIA INDUCTION FURNACE Application filed January 8, 1930, Serial No. 419,437, and in Great Britain January 8, 1929.

fi means for, and, more particularly, a method of, sintering the lining of an electric-induction' furnace.

In practicing my invention, I provide a furnace casing, an induction coil located therein in a rammed-in lining, and I provide further, a metal template for initially limiting 'or defining the internal dimensions of the rammed-in lining, as well as a ring of metal located at the upper end of the furnace lining.

In the single sheet of drawings,

Figure l is a view, in vertical lateral section through an induction-furnace assembly ready for its initial operation, and

Fig. 2 is a sectional view of one element of the furnace after the first melting operation in the furnace has been completed.

Furnace linings or crucibles have heretofore been repared in coreless induction furnaces of the surrounded-pool type by assembling a refractory material capable of being sintered, such as silica or magnesite, with or without a binder, within and around the inductor coil, and sintering such material by heating either a metallic charge or a metallic template or liner, or both, by induction. It has been found, in practice, however, that it is difficult, if not impossible, to adequately sinter the top portion or mouth of the lining or crucible by this method.

'In order to properly sinter, not onlythe main-or body portion of the lining but also the top portion thereof, I provide, in addition to a metal template, an annular member of relatively larger area of cross section than the template and located at the top of the furnace. This ring of metal is of such large area of cross-section that it is not melted by the eddy currents induced therein when the inductor of the furnace is energized but is effective to properly sinter that portion of the lining with which it is in operative engagement.

A metal casing 11 is shown for purpose of illustration and to define the outer contour of the furnace, although it is not essential to my invention that such a casing be employed. Within this outer casing is located a rammed-in lining 12 which may be made of silica or magnesite. The melting chamber 13 is defined by a template 14: which is of substantially tubular or of pot shape and is made of relatively thin metal which may be steel or iron, in accordance with the kind of metal to be melted in the furnace.

An inductor coil 16 is provided which comprises a suitable number of turns of an electric conductor, here shown as being substantially of rectangular shape in lateral section, the individual turns of which are separated from each other by suitable insulating material 17. I have indicated the inductor coil generally only as its specific construction and location constitute no part of my present invention. Any suitable inductor coil may be employed.

The top portion of the lining 12 extends some distance above the upper turns of the inductor coil, and incomplete rings 18 of a suitable electric-insulating material may be located between the top of the inductor coil and a cover member 19 which may also be in the form of an incomplete ring resting upon the top edge of the casing 11.

A pouring s out 21 is provided, the bottom portion 01. which may be filled with a material 22, such as ganister, which is initially plastic and is frequently used as material for lining a pouring spout.

An initially complete metal ring 23 is provided at the top portion of the crucible to rest upon the top of the template 14, the lining material being worked or rammed into intimate contact with this ring of metal.

For the purpose of sintering the crucible or lining, a charge of metal to be melted, such as steel or iron, may be placed within the template i l, the inductor coil may then be energized and the charge and the template 14 heated, whereby the lining in contact with the template is sintered in a known manner.

During the preliminary stages of heating, as set forth above, the ring of material 23 1s electro-magnetically shielded by the template 14 to a large extent and, therefore, but

little heat is generated therein. The template 14.- which, as was hereinabove stated,

is preferably made of the same material as is to be initially melted in the furnace, will itself melt at some time during the operation of the furnace, and the electro-magnetic shielding of the, ring 23 is decreased until a considerable amount of heat is generated or developed in the ring 23, whereby the upper portion of the lining with which it is in immediate contact is heated and sintered. As the melting operation continues, the'top ring is again shielded by the molten charge.

When the molten metal is ready to be poured, the furnace is tilted by suitable means (not shown in the drawings) so that the molten metal will engage the lower part of the ring, 23 adjacent to the pouring lip or spout at the point indicated by 24:. The ring will, therefore, be melted at this place and a recess will be formed therein, as is indicated by 26, in Fig. 2 of the drawings, so'that the molten metal will be permitted to run out at 25 the pouring spout between the upper portion of the ring 23 and the lining 22.

The molten metal flowing past the metallic ring through the spout will carry with it a portion of the ring, leaving a constricted portion, 'as indicated by the numeral 27 in Fig. 2 of the drawings. When the furnace is recharged and a second melting process is begun, eddy currents will flow in the metal ring 23 and, as the point of hi hest resistance 5 is that indicated by 27 in Fig. 2, this portion of the ring will melt and interrupt the continuity thereof, after which little or no heat will be developed therein, as there is no closed circuit through which the eddy currents may flow.

The heat developed in the ring 23 is not as large as that developed in the template 14 immediately within the inductor coil 16, and the sintering process is, therefore, not carried to as high a degree as is the case farther down in the furnace, and this lining would, therefore, be liable to crumble during service. One of the particular results which may occur is that the width of the pouring spout will be decreased and this decrease in width may be sufiicient to cause trouble. The metal ring 23, which is initially a complete annulus and is finally an open or incomplete annulus, servesalso to prevent expansion of the lining or movement thereof to constrict the lateral width of the pouring spout, as well as serving as a mechanical support for the upper part of the lining with which it is in immediate engagement.

While I have illustrated and described a specific embodiment of a furnace structure, I do not desire to be limited thereto, as such illustration is provided for the purpose of 65 illustrating a complete structure, and variations may be made in the assembly without departing from the spirit and S00 e of my invention, and it is desired, there ore, that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. The method of sinterin a predetermined portion of the lining 0 an induction furnace having an inductor coil which comprises locating a metal ring of relatively large area of cross section at that portion of the lining, heating the same by induction from the induction coil simultaneously with the heating of a charge, reducing the area of cross section of the ring at a predetermined point by pouring molten metal past said point, andv then splitting said ring by the inductive effect of the energized coil.

2. The method of sintering the top portion of the lining of an electric-induction furnace having an energized coil which comprises locating a metal ring within the linin at the top portion thereof, inductively heatlng the same from the energizing coil at its initial energization, simultaneously with the melting of an initial charge of metal in the furnace, reducing the area of cross section of said metal ring at a predetermined point by pouring the molten charge from the furnace and then splitting said ring by a second en-- ergization of the coil.

3. The method of sintering the to portion of the lining of an electric-in uction furnace having an energizing coil and a pouring spout and providing a support for the upper portion of the lining to maintain a predetermined width of spout which comprises locating a metal ring of relatively large area of cross section at the top portion of the crucible lining to substantially close said pouring spout, energizing the coil to inductively heat said ring to sinter the lining engaged thereby and a charge to melt the same, pourng the molten metal from said furnace to melt away a part of the ring directly above the spout, and reenergizing the coil to heat the rin until it splits at the point of reduced sectlon.

4. In an electric-induction furnace having a refractory lining, a pouring spout at the top of the lining and an energizing coil, the method of sintering the top portion of the lining and providing a permanent spreading ring to maintain a predetermined shape of the spout which comprises locating a metal ring at the top of the lining of such area of cross section that it will be heated to a temperature below its melting point whereby to sinter the lining adjacent to it upon initial energization of the coil to melt a charge in the furnace, pouring the molten metal through the pouring spout past the ring to reduce the area of the ring over the spout by contact with the molten metal, and

then reenergizing the coil to cause inductive heating of the ring and melting thereof at the place of reduced area;

In testimony whereof, I have hereunto subscribed my name this twenty-third day of December, 1929.

NEVILLE RYLAND DAVIS. 

